1. Field of the Invention
The present invention relates to a characteristic X-ray detecting device utilizable for the detection of substances in a testpiece.
2. Description of the Prior Art
The characteristic X-ray detecting device is well known as an instrument for detecting substances contained in a testpiece. The detection is generally carried out by exciting the testpiece with radiation and then by analyzing the wavelength of characteristic X-rays (i.e., fluorescent X-rays) emitted from the excited testpiece. The conventional characteristic X-ray detecting device generally comprises a substantially closed vessel having an X-ray incident window defined therein and closed by a lid made of beryllium or the like. The closed vessel contains therein an X-ray detector utilizing, for example, a semiconductor.
With the conventional characteristic X-ray detecting device, a problem has been found in that, when an attempt is made to detect secondary X-rays emitted from a testpiece to be analyzed as a result of excitation of the testpiece with primary X-rays while the detecting device has been positioned close to a surface of the testpiece, one or both of the primary X-rays used for the excitation of the testpiece to be analyzed and of the secondary X-rays (including characteristic X-rays and scattered X-rays) emitted from the testpiece may enter the closed vessel and subsequently impinge upon the inner surface of the closed vessel, resulting in an erroneous measurement induced by X-rays coming from the inner surface excited by the primary or secondary X-rays.